The invention relates to the purification of polyaminocarboxylate chelating agents which can be used as MRI contrast agents. Polyaminocarboxylates are part of several drugs which include gadoteric acid, gadobutrol, gadobenic acid, gadopentetate, gadoversetamide, gadodiamide. The key ingredient to all the gadolinium based drugs is the chelate to which the gadolinium binds. Having a highly pure chelate free of any salts and metals is the basis for the preparation of the pure gadolinium based MRI agents.
Some of the chelates include 1,4,7,10-tetraazocyclododecane-, 1,4,7,10-tetraacetic acid (DOTA) for gadoteric acid, Pentetic acid (DTPA) for gadopentetate, BOPTA for gadobenic acid, 10-(1-hydroxymethyl-2,3-dihydroxypropyl)-1,4,7-tris(carboxymethyl)-1,4,7,10 tetraazocyclododecane (DO3A-butrol) for gadobutrol.